1. Field of the Invention
The present invention relates to a blow-molded plastic part having a non-reinforced plastic strip integrally molded therein to form a durable living hinge.
2. Background Art
Plastic components sometimes require significant load-bearing characteristics, such as in vehicle load floors and the like. In order to provide these load-bearing characteristics the plastic material may be reinforced by glass filling for example. However, this filling may also render the part brittle and not suitable for a living hinge.
It is also sometimes desirable to provide an integral hinge in the reinforced plastic component to allow respective bending of adjacent portions of the plastic component, for example to form a pivotable door for access to a spare tire storage compartment or the like. Because reinforced materials are so brittle, a living hinge typically cannot be formed in the material to allow pivoting, therefore metal hinges have been used in such applications. However, metal hinges result in significant material and labor costs. It is therefore desirable to provide a method of forming a reinforced plastic part with a hinge in which manufacturing costs are reduced.
The present invention provides a method of manufacturing a reinforced plastic part, such as a glass-filled plastic part, wherein a living hinge is formed by integrally molding an unfilled plastic strip in the part to form the living hinge.
More specifically, the present invention provides a method of forming a carpeted plastic part wherein a carpet is positioned between first and second mold halves. A non-reinforced plastic strip is positioned adjacent a portion of the back surface of the carpet. A hollow parison of reinforced plastic material is positioned between the first and second mold halves. The first and second mold halves are closed together to form a carpeted plastic part having a thinned-down region of the reinforced plastic material adjacent the plastic strip such that the plastic strip is sandwiched between the thinned-down region and the carpet to form a flexible living hinge.
Preferably, the non-glass-filled plastic strip is a biaxially oriented plastic material which is stretchable along two axes, such as a polypropylene material.
The present invention could be used for forming a living hinge in any stiff material, such as a glass-filled plastic, mica-filled plastic, talc-filled plastic or other structurally reinforced plastic material.
The non-reinforced plastic strip may be positioned between the carpet and the parison, or it may be positioned on the opposite side of the parison from the carpet.
Accordingly, an object of the invention is to provide a method of forming a durable living hinge in a load-bearing plastic component.
A further object of the invention is to provide a method of forming a durable living hinge in a carpeted load-bearing plastic part, such as a vehicle load floor, in a manner in which manufacturing costs are reduced.
The above objects and other objects, features and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.